1. Field of the Invention
This invention relates to a digital camera with dualpriority and program automatic exposure controls and, more particularly, to a system for providing the various display and setting conditions of such a camera in selective and/or corrective manner.
2. Description of the Prior Art
It is already known in the prior art to provide a camera equipped with a shutter preselection automatic diaphragm range and a diaphragm preselection automatic shutter range which are set in a selective manner by taking into account their respective advantages. The former exposure control is convenient in snapshot and sport photography where camera shake or the formation of blurred images of subjects of principal photographic interest has to be avoided. The latter enables the photographer to adjust, in advance, the depth of field which is quite important in portrait, close-up and copying photography. Since the exposure value is a function of scene brightness, there is a strong possibility for the light value to fall outside of the dynamic range of the diaphragm setting or the shutter timing control. If this occurs, the photographer must alter the preset value of shutter time or diaphragm aperture until a correct exposure value is derived. This necessary manipulation is somewhat time-consuming and, therefore, will sometimes result in missing a good shutter opportunity that will never again recur.
It is also known to provide a program camera in which shutter time and diaphragm aperture are automatically set mutually or alternately in accordance with a predetermined program. While this exposure control is capable of deriving exposure values over the entire range of photographic situations which may be encountered, skilled photographers cannot always apply their full knowledge of the influence of shutter times or diaphragm aperture to the quality of exposures.
An attempt has been made to solve the complementary problems of these two types of cameras by incorporating all of the aforementioned exposure controls in a single camera. In this case, however, a more stringent requirement is placed on the rapid access of setting not only a desired mode but also a preselected exposure factor. It is also necessary to set the sensitivity of the film used into the camera. As long as the manual settings are performed by analog means such as the shutter and film dials, diaphragm ring and mode selection control knob, the necessary manipulation of these setting means becomes very complicated. This is particularly so when the number of program schemes employed is not limited to a single program but is increased to contain shutter preselection and diaphragm preselection magic modes, and the photographer, therefore, will often be misled when two or more mode symbols are displayed at a time. It is desirable to shield not only all of the mode symbols available except for the current one, but also all of the graduations for the shutter time, diaphragm aperture and film speed scales except for the selected values. However, this calls for an increase in the complexity and size of the camera housing structure. What is even worse is that the decorative aspect of the camera, which is of great importance in the market of this kind of item, is adversely affected.
Accordingly, the present invention has, for a general object, the incorporation of the dual-priority and program automatic exposure modes in a common camera, while nevertheless eliminating all of the above-mentioned drawbacks.
An object of the present invention is to provide a camera having incorporated therein a mode selection device receptive of one of a number of setting members corresponding to the number of automatic exposure modes available from the outside of the camera housing and responsive to the information on the received setting member for providing outputs to control the shutter timing and diaphragm setting devices of the camera in accordance with the selected mode.
According to one embodiment of the invention, as is applied to a digital control system for the shutter timing and diaphragm setting devices, the mode selection device is constructed in the form of a logic circuit rendered responsive to information coded in binary form on the setting member.
Another object of the present invention is to provide a camera of the character described above with a single operating member for a number of display and setting conditions corresponding to the number of automatic exposure modes available.
To achieve these objects, the present invention incorporates the use of a counter in combination with a pulse generator which also serves to digitally display and set the values of shutter time, diaphragm aperture, film speed and film footage. When no setting member is present in the camera, actuation of the operating member or push button causes the counter to cooperate with the pulse generator so that all of the mode symbols are sequentially displayed. Upon release of the button, the current mode is set. When the setting member is supplied to the camera, the counter is no longer efffective to count the pulses from the generator but, instead, is rendered responsive to the information on the setting member.
Another object of the invention is to provide a digital camera of smart appearance with a number of controlling push buttons necessary to symbolically display all of the exposure factors on the upper panel of the camera housing as well as in the field of view of the finder and to select and/or correct the values of the exposure factors displayed. The push buttons are to be neatly arranged to reduce the possibility of erroneous manipulation.
Another object of the invention is to display the number of film frames available and the number of frames exposed and to sound an alarm when a few fresh frames are reached.
Another object of the invention is to utilize the sound alarming device in facilitating actuation and release of each of the set buttons. In this connection, a sound signal of short duration is heard each time the displayed discrete value advances one graduation.
In accordance with the invention, an automatic exposure control apparatus for a camera comprises light measuring means for producing an electrical signal proportional to the level of brightness of an object being photographed, exposure factor setting means for producing electrical signals proportional to preset values of exposure factors, and exposure value computing means responsive to the electrical signals from the light measuring and the factor setting means for producing an output. Also included are shutter control means, diaphragm control means and exposure mode selecting means responsive to first and second switch signals for directing the output of the computing means to either of the shutter control means and the diaphragm control means, respectively. Finally included are signal forming means having terminals receptive of one of a number of different mode setting members and upon reading of information on said mode setting member, for producing either of one of the first and second signals to be applied to the mode selecting means.
For a better understanding of the present invention, reference is made to the following description and accompanying drawings, while the scope of the present invention will be pointed out in the appended claims.